RESEARCH ARTICLE Open Access Insights into the European rabbit (Oryctolagus

cuniculus) innate immune system: genetic diversity of the toll-like receptor 3 (TLR3) in wild populations and domestic breeds Joana Abrantes1,3, Helena Areal1,2 and Pedro J Esteves1,4* Background: Toll-like receptors (TLRs) belong to the innate immune system and are a major class of pattern recognition receptors representing the first line of the innate immune response. The TLR molecule is structurally composed by an ectodomain that contains leucine rich repeats (LRRs) that interact with pathogen associated molecular patterns (PAMPs), a transmembrane domain and a conserved cytoplasmic domain designated TIR (Toll-IL1 receptor) that is responsible for the intracellular signaling. TLR3 has been associated with the direct recognition of double-stranded viral RNA resulting from viral replication, while TLR7 and TLR8 target single-stranded viral RNA. In the European rabbit (Oryctolagus cuniculus), TLR7 and TLR8 were reported to be absent and pseudogenised, respectively, making TLR3 the only available TLR for the recognition of viral RNA. Thus, the levels of diversity of TLR3 were evaluated in the European rabbit by analysing different genetic backgrounds and exposure to pathogen pressures. Results: We detected 41 single nucleotide polymorphisms (SNPs) in the coding sequence of TLR3. The highest diversit